1. Field of the Invention
The invention relates to a card device with a fingerprint sensor, and more particularly to a card device with a sweep-type fingerprint sensor.
2. Description of the Related Art
In order to prevent the syndicate from counterfeiting the smart cards such as credit cards, personal identification cards, driver's licenses, passports, social welfare cards and health insurance cards, every card issuer has to spend a lot of resource to protect the smart cards with strict security designs. Because the fingerprint is the personal biometric data and cannot be easily counterfeited, the smart card embedded with the fingerprint sensor becomes one of the mainstream development in the future.
All the fingerprint sensors embedded in the conventional card devices belong to the two-dimensional (2D) sensor. That is, the fingerprint sensor can acquire the finger's fingerprint image as long as the finger statically contacts the fingerprint sensor. For instance, the card devices disclosed in U.S. Pat. Nos. 4,582,985 and 6,494,380 utilize the 2D fingerprint sensors. Owing to the dimensional limitation of the finger, the sensing area of the conventional 2D fingerprint sensor is at least greater than 9 mm*9 mm. Furthermore, owing to the limitation in the dimension of silicon wafer, only 50 to 70 effective chips may be produced in a 6″ wafer. The selling price of the single fingerprint sensor is at least greater than 10 U.S.D. with the packaging and testing costs included therein, which will limit the usage of the card device embedded with the fingerprint sensor.
Because the smart card is a portable device, the user may unintentionally apply external forces to the smart card to make it bent or twisted. In this condition, the fingerprint sensor embedded in the smart card may be caused an extreme stress and thus damaged or even fractured. In order to solve the above-mentioned problem, U.S. Pat. No. 6,494,380 discloses a 2D fingerprint sensor that is also composed of a plurality of sensing blocks. Although the problem of the sensor damage in the twisted or curved card device such as the smart card may be solved, the fingerprint image distortion will be caused owing to the spacing between two adjacent sensing blocks. When the most important minutia pattern of the fingerprint is located in the spacing, the fingerprint identifying operation cannot be really completed.
Thus, it is an important subject to provide a low-cost card device (e.g., a smart card) embedded with a fingerprint sensor that cannot be easily damaged.